The present invention relates to a registration system that registers an electronic key to a controller of a communication subject.
A known electronic key system performs wireless communication between a vehicle and an electronic key, which is held by a user of the vehicle to lock and unlock doors or start and stop the engine when the electronic key is verified. In such an electronic key system, the communication between the electronic key and the vehicle is encrypted and thereby protected to maintain a certain level of security (for example, refer to Japanese Laid-Open Patent Publication No. 2009-302848).
Encrypted communication may be performed by employing symmetric-key cryptosystem that uses the same encryption key for encryption and decryption. A shared key, that is, the same encryption key, is registered to an electronic key and a vehicle that perform encrypted communication in compliance with the symmetric-key cryptosystem. The registration of the encryption key to the electronic key and the vehicle is performed when registering the electronic key to a controller of the vehicle. The controller verifies the electronic key by comparing identification information received from the electronic key with identification information stored in its memory.
In an electronic key registration system that registers an electronic key to a controller, to avoid registration of an electronic key other than that of the user, the inventors of the present invention have considered storing in advance a vehicle ID code (identification information unique to a communication subject) of a vehicle (communication subject) to the controller and the electronic key, and then shipping the controller and the electronic key together out of a factory. In this example, however, the shipping becomes complicated, and an additional electronic key cannot be registered at a later date. The inventors of the present invention have also considered shipping out the controller, which stores a vehicle ID, and the electronic key separately from a factory. However, in this case, someone may tamper with the vehicle ID code. Such a problem is not limited to an electronic key system used in a vehicle and may also occur in an electronic key system used in a building such as a house.